Ruthenium‐Promoted Acceptor‐less Dehydrogenation of a Germane

The transition metal‐mediated activation of element–hydrogen bonds is an important goal for the preparation of commodity chemical compounds and novel materials. Here a facile route to the activation of germanium‐hydrogen bonds, based on the spontaneous elimination of dihydrogen, is reported. This represents a mechanistic divergence from the established methods for Ge─H bond cleavage. The novel complexes [Ru(η 5 ‐C 5 H 5 )(OTf)(PPh 3 ) 2 ] and [{Ru(η 5 ‐C 5 H 5 )(dppe)} 2 (μ‐N 2 )]OTf 2 are central to the success of this route. These crystalline species may be prepared in high yield and are highly effective sources of the 16‐electron [Ru(η 5 ‐C 5 H 5 )(P) 2 ] + fragment. Both complexes react with GeH 2 Ph 2 to eliminate H 2 and afford [Ru(η 5 ‐C 5 H 5 )(GePh 2 OTf)(P) 2 ] [(P) 2 = 2 PPh 3 , dppe], which is best described as a triflate‐stabilized metallogermylenium complex. Different species are observed on initial treatment of [Ru(η 5 ‐C 5 H 5 )(OTf)(PPh 3 ) 2 ] or [{Ru(η 5 ‐C 5 H 5 )(dppe)} 2 (μ‐N 2 )]OTf 2 with GeH 2 Ph 2 . In the dppe case, a σ‐germane complex is identified, which is proposed to undergo spontaneous elimination of H 2 : a key step in the double Ge─H bond activation, promoted by the sterically demanding half‐sandwich ruthenium complexes. This represents a distinct pathway for Ge─H bond activation when compared to the established routes, such as deprotonation by a basic hydrocarbyl ligand or oxidative addition, leading the way to new pathways to functionalize organogermanium compounds.